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        data-chapter-title="scrapy中的middlewares"
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        <li class="chapter " data-level="1" data-path="认识爬虫/introduceSpider.html">
            
                
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                            <b>1.</b>
                        
                        认识爬虫
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                            <b>1.1.</b>
                        
                        HTTP
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                            <b>1.2.</b>
                        
                        requests
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                            <b>1.3.</b>
                        
                        初步爬虫小项目
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                            <b>2.</b>
                        
                        正则表达式
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                            <b>2.1.</b>
                        
                        正则表达式练习
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                            <b>2.2.</b>
                        
                        正则表达式之后的第一个项目
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                            <b>2.3.</b>
                        
                        正则表达式常用表
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                            <b>2.4.</b>
                        
                        正则表达式重点
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                            <b>2.5.</b>
                        
                        正则表达式常问问题
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                            <b>2.6.</b>
                        
                        正则爬虫项目练习
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        <li class="chapter " data-level="3" data-path="XPATH/xpath-in.html">
            
                
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                            <b>3.</b>
                        
                        XPATH
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                            <b>3.1.</b>
                        
                        XPATH认识
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                            <b>3.2.</b>
                        
                        XPATH的代码例子
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                            <b>3.3.</b>
                        
                        XPATH的爬虫练习
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                            <b>4.</b>
                        
                        BeautifulSoup
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                            <b>4.1.</b>
                        
                        常用的css选择器
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                            <b>4.2.</b>
                        
                        BeautifulSoup4的各种例子
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                            <b>5.</b>
                        
                        ip代理池项目
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                            <b>6.</b>
                        
                        Selenium
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                            <b>7.</b>
                        
                        进程线程协程
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                            <b>7.1.</b>
                        
                        gevent
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                            <b>7.2.</b>
                        
                        green_let
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                            <b>7.3.</b>
                        
                        yield
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                            <b>7.4.</b>
                        
                        multiprecessing
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        <li class="chapter " data-level="7.5" data-path="进程线程协程/threading.html">
            
                
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                            <b>7.5.</b>
                        
                        threading
                    </a>
            
            
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        <li class="chapter " data-level="8" data-path="scrapy框架/scrapy.html">
            
                
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                            <b>8.</b>
                        
                        Scrapy
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                            <b>8.1.</b>
                        
                        scrapy_setting
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        <li class="chapter " data-level="8.2" data-path="scrapy框架/模块作用.html">
            
                
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                            <b>8.2.</b>
                        
                        模块作用
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        <li class="chapter " data-level="8.3" data-path="scrapy框架/19个中间件.html">
            
                
                    <a href="../scrapy框架/19个中间件.html">
                
                        <i class="fa fa-check"></i>
                        
                            <b>8.3.</b>
                        
                        19个中间件
                    </a>
            
            
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        </li>
    
        <li class="chapter " data-level="9" data-path="scrapy-redis分布式/scrapy-redis.html">
            
                
                    <a href="../scrapy-redis分布式/scrapy-redis.html">
                
                        <i class="fa fa-check"></i>
                        
                            <b>9.</b>
                        
                        scrapy-redis分布式
                    </a>
            
            
            <ul class="articles">
                
    
        <li class="chapter " data-level="9.1" data-path="scrapy-redis分布式/scrapy-redis的改造方法.html">
            
                
                    <a href="../scrapy-redis分布式/scrapy-redis的改造方法.html">
                
                        <i class="fa fa-check"></i>
                        
                            <b>9.1.</b>
                        
                        scrapy-redis的改造方法
                    </a>
            
            
        </li>
    

            </ul>
            
        </li>
    
        <li class="chapter " data-level="10" data-path="spider_projects/introduce.html">
            
                
                    <a href="../spider_projects/introduce.html">
                
                        <i class="fa fa-check"></i>
                        
                            <b>10.</b>
                        
                        spider_projects
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        <li class="chapter " data-level="10.1" data-path="spider_projects/使用代理在普通爬虫脚本下.html">
            
                
                    <a href="../spider_projects/使用代理在普通爬虫脚本下.html">
                
                        <i class="fa fa-check"></i>
                        
                            <b>10.1.</b>
                        
                        使用代理在普通爬虫脚本下
                    </a>
            
            
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        <li class="chapter " data-level="10.2" data-path="spider_projects/xpath爬取前程无忧的数据.html">
            
                
                    <a href="../spider_projects/xpath爬取前程无忧的数据.html">
                
                        <i class="fa fa-check"></i>
                        
                            <b>10.2.</b>
                        
                        xpath爬取前程无忧的数据
                    </a>
            
            
        </li>
    
        <li class="chapter " data-level="10.3" data-path="spider_projects/存储数据库的脚本.html">
            
                
                    <a href="../spider_projects/存储数据库的脚本.html">
                
                        <i class="fa fa-check"></i>
                        
                            <b>10.3.</b>
                        
                        存储数据库的脚本
                    </a>
            
            
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        <li class="chapter " data-level="10.4" data-path="spider_projects/weibo.html">
            
                
                    <a href="../spider_projects/weibo.html">
                
                        <i class="fa fa-check"></i>
                        
                            <b>10.4.</b>
                        
                        爬取央视新闻微博
                    </a>
            
            
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        <li class="chapter " data-level="10.5" data-path="spider_projects/weibo2.html">
            
                
                    <a href="../spider_projects/weibo2.html">
                
                        <i class="fa fa-check"></i>
                        
                            <b>10.5.</b>
                        
                        爬取明星的微博
                    </a>
            
            
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        <li class="chapter " data-level="10.6" data-path="spider_projects/liepin.html">
            
                
                    <a href="../spider_projects/liepin.html">
                
                        <i class="fa fa-check"></i>
                        
                            <b>10.6.</b>
                        
                        爬取猎聘的职位信息Crawl
                    </a>
            
            
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        <li class="chapter " data-level="10.7" data-path="spider_projects/zhilianRe.html">
            
                
                    <a href="../spider_projects/zhilianRe.html">
                
                        <i class="fa fa-check"></i>
                        
                            <b>10.7.</b>
                        
                        纯正则爬取智联的职位信息
                    </a>
            
            
        </li>
    
        <li class="chapter " data-level="10.8" data-path="spider_projects/setting.html">
            
                
                    <a href="../spider_projects/setting.html">
                
                        <i class="fa fa-check"></i>
                        
                            <b>10.8.</b>
                        
                        scrapy中的setting
                    </a>
            
            
        </li>
    
        <li class="chapter " data-level="10.9" data-path="spider_projects/items.html">
            
                
                    <a href="../spider_projects/items.html">
                
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                            <b>10.9.</b>
                        
                        scrapy中的items
                    </a>
            
            
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        <li class="chapter " data-level="10.10" data-path="spider_projects/pipeline.html">
            
                
                    <a href="../spider_projects/pipeline.html">
                
                        <i class="fa fa-check"></i>
                        
                            <b>10.10.</b>
                        
                        scrapy中的pipeline
                    </a>
            
            
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        <li class="chapter active" data-level="10.11" data-path="spider_projects/middlewares.html">
            
                
                    <a href="../spider_projects/middlewares.html">
                
                        <i class="fa fa-check"></i>
                        
                            <b>10.11.</b>
                        
                        scrapy中的middlewares
                    </a>
            
            
        </li>
    
        <li class="chapter " data-level="10.12" data-path="spider_projects/框架中的代码运行脚本.html">
            
                
                    <a href="../spider_projects/框架中的代码运行脚本.html">
                
                        <i class="fa fa-check"></i>
                        
                            <b>10.12.</b>
                        
                        框架中的代码运行脚本
                    </a>
            
            
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        <li class="chapter " data-level="11" data-path="爬虫的面试题/面试题1-10.html">
            
                
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                            <b>11.</b>
                        
                        爬虫面试题
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                        <h1 id="&#x4E2D;&#x95F4;&#x4EF6;&#x7684;&#x8BBE;&#x7F6E;-&#x4EE3;&#x7406;">&#x4E2D;&#x95F4;&#x4EF6;&#x7684;&#x8BBE;&#x7F6E; &#x4EE3;&#x7406;</h1>
<pre><code class="lang-python"><span class="hljs-comment"># -*- coding: utf-8 -*-</span>

<span class="hljs-comment"># Define here the models for your spider middleware</span>
<span class="hljs-comment">#</span>
<span class="hljs-comment"># See documentation in:</span>
<span class="hljs-comment"># https://doc.scrapy.org/en/latest/topics/spider-middleware.html</span>

<span class="hljs-keyword">from</span> scrapy <span class="hljs-keyword">import</span> signals
<span class="hljs-keyword">from</span> twisted.internet.defer <span class="hljs-keyword">import</span> DeferredLock
<span class="hljs-keyword">import</span> base64

<span class="hljs-class"><span class="hljs-keyword">class</span> <span class="hljs-title">ProjectsSpiderMiddleware</span><span class="hljs-params">(object)</span>:</span>
    <span class="hljs-comment"># Not all methods need to be defined. If a method is not defined,</span>
    <span class="hljs-comment"># scrapy acts as if the spider middleware does not modify the</span>
    <span class="hljs-comment"># passed objects.</span>

<span class="hljs-decorator">    @classmethod</span>
    <span class="hljs-function"><span class="hljs-keyword">def</span> <span class="hljs-title">from_crawler</span><span class="hljs-params">(cls, crawler)</span>:</span>
        <span class="hljs-comment"># This method is used by Scrapy to create your spiders.</span>
        s = cls()
        crawler.signals.connect(s.spider_opened, signal=signals.spider_opened)
        <span class="hljs-keyword">return</span> s

    <span class="hljs-function"><span class="hljs-keyword">def</span> <span class="hljs-title">process_spider_input</span><span class="hljs-params">(self, response, spider)</span>:</span>
        <span class="hljs-comment"># Called for each response that goes through the spider</span>
        <span class="hljs-comment"># middleware and into the spider.</span>

        <span class="hljs-comment"># Should return None or raise an exception.</span>
        <span class="hljs-keyword">return</span> <span class="hljs-keyword">None</span>

    <span class="hljs-function"><span class="hljs-keyword">def</span> <span class="hljs-title">process_spider_output</span><span class="hljs-params">(self, response, result, spider)</span>:</span>
        <span class="hljs-comment"># Called with the results returned from the Spider, after</span>
        <span class="hljs-comment"># it has processed the response.</span>

        <span class="hljs-comment"># Must return an iterable of Request, dict or Item objects.</span>
        <span class="hljs-keyword">for</span> i <span class="hljs-keyword">in</span> result:
            <span class="hljs-keyword">yield</span> i

    <span class="hljs-function"><span class="hljs-keyword">def</span> <span class="hljs-title">process_spider_exception</span><span class="hljs-params">(self, response, exception, spider)</span>:</span>
        <span class="hljs-comment"># Called when a spider or process_spider_input() method</span>
        <span class="hljs-comment"># (from other spider middleware) raises an exception.</span>

        <span class="hljs-comment"># Should return either None or an iterable of Response, dict</span>
        <span class="hljs-comment"># or Item objects.</span>
        <span class="hljs-keyword">pass</span>

    <span class="hljs-function"><span class="hljs-keyword">def</span> <span class="hljs-title">process_start_requests</span><span class="hljs-params">(self, start_requests, spider)</span>:</span>
        <span class="hljs-comment"># Called with the start requests of the spider, and works</span>
        <span class="hljs-comment"># similarly to the process_spider_output() method, except</span>
        <span class="hljs-comment"># that it doesn&#x2019;t have a response associated.</span>

        <span class="hljs-comment"># Must return only requests (not items).</span>
        <span class="hljs-keyword">for</span> r <span class="hljs-keyword">in</span> start_requests:
            <span class="hljs-keyword">yield</span> r

    <span class="hljs-function"><span class="hljs-keyword">def</span> <span class="hljs-title">spider_opened</span><span class="hljs-params">(self, spider)</span>:</span>
        spider.logger.info(<span class="hljs-string">&apos;Spider opened: %s&apos;</span> % spider.name)


<span class="hljs-class"><span class="hljs-keyword">class</span> <span class="hljs-title">ProjectsDownloaderMiddleware</span><span class="hljs-params">(object)</span>:</span>
    <span class="hljs-comment"># Not all methods need to be defined. If a method is not defined,</span>
    <span class="hljs-comment"># scrapy acts as if the downloader middleware does not modify the</span>
    <span class="hljs-comment"># passed objects.</span>
    <span class="hljs-function"><span class="hljs-keyword">def</span> <span class="hljs-title">__init__</span><span class="hljs-params">(self)</span>:</span>
        self.lock = DeferredLock()
        self.proxy = <span class="hljs-string">&apos;&apos;</span>
        self.need_chnage_proxy = <span class="hljs-keyword">True</span>

<span class="hljs-decorator">    @classmethod</span>
    <span class="hljs-function"><span class="hljs-keyword">def</span> <span class="hljs-title">from_crawler</span><span class="hljs-params">(cls, crawler)</span>:</span>
        <span class="hljs-comment"># This method is used by Scrapy to create your spiders.</span>
        s = cls()
        crawler.signals.connect(s.spider_opened, signal=signals.spider_opened)
        <span class="hljs-keyword">return</span> s

    <span class="hljs-function"><span class="hljs-keyword">def</span> <span class="hljs-title">process_request</span><span class="hljs-params">(self, request, spider)</span>:</span>
        <span class="hljs-comment"># Called for each request that goes through the downloader</span>
        <span class="hljs-comment"># middleware.</span>
        self.lock.acquire()
        <span class="hljs-keyword">if</span> self.need_chnage_proxy:
            self.proxy = self.new_proxy()
            self.need_chnage_proxy = <span class="hljs-keyword">False</span>
        request.meta[<span class="hljs-string">&apos;proxy&apos;</span>] = self.proxy
        print(self.proxy)
        self.lock.release()

        <span class="hljs-comment"># Must either:</span>
        <span class="hljs-comment"># - return None: continue processing this request</span>
        <span class="hljs-comment"># - or return a Response object</span>
        <span class="hljs-comment"># - or return a Request object</span>
        <span class="hljs-comment"># - or raise IgnoreRequest: process_exception() methods of</span>
        <span class="hljs-comment">#   installed downloader middleware will be called</span>
        <span class="hljs-keyword">return</span> <span class="hljs-keyword">None</span>

    <span class="hljs-function"><span class="hljs-keyword">def</span> <span class="hljs-title">process_response</span><span class="hljs-params">(self, request, response, spider)</span>:</span>
        <span class="hljs-comment"># Called with the response returned from the downloader.</span>
        self.lock.acquire()
        <span class="hljs-keyword">if</span> response.status != <span class="hljs-number">200</span>:
            self.need_chnage_proxy = <span class="hljs-keyword">True</span>
            self.lock.release()
            <span class="hljs-keyword">return</span> request
        self.lock.release()
        <span class="hljs-comment"># Must either;</span>
        <span class="hljs-comment"># - return a Response object</span>
        <span class="hljs-comment"># - return a Request object</span>
        <span class="hljs-comment"># - or raise IgnoreRequest</span>
        <span class="hljs-keyword">return</span> response

    <span class="hljs-function"><span class="hljs-keyword">def</span> <span class="hljs-title">process_exception</span><span class="hljs-params">(self, request, exception, spider)</span>:</span>
        <span class="hljs-comment"># Called when a download handler or a process_request()</span>
        <span class="hljs-comment"># (from other downloader middleware) raises an exception.</span>
        self.lock.acquire()
        self.need_chnage_proxy = <span class="hljs-keyword">True</span>
        self.lock.release()
        <span class="hljs-comment"># Must either:</span>
        <span class="hljs-comment"># - return None: continue processing this exception</span>
        <span class="hljs-comment"># - return a Response object: stops process_exception() chain</span>
        <span class="hljs-comment"># - return a Request object: stops process_exception() chain</span>
        <span class="hljs-keyword">pass</span>

    <span class="hljs-function"><span class="hljs-keyword">def</span> <span class="hljs-title">spider_opened</span><span class="hljs-params">(self, spider)</span>:</span>
        spider.logger.info(<span class="hljs-string">&apos;Spider opened: %s&apos;</span> % spider.name)

    <span class="hljs-function"><span class="hljs-keyword">def</span> <span class="hljs-title">new_proxy</span><span class="hljs-params">(self)</span>:</span>
        url = <span class="hljs-string">&apos;http://dps.kdlapi.com/api/getdps/?orderid=923732543439561&amp;num=1&amp;pt=1&amp;ut=1&amp;dedup=1&amp;sep=1&apos;</span>
        <span class="hljs-keyword">import</span> requests
        response = requests.get(url)
        <span class="hljs-keyword">return</span> <span class="hljs-string">&apos;http://&apos;</span> + response.text
</code></pre>

                    
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